Imaging unit

ABSTRACT

An imaging unit includes a housing having an opening; a positioning portion provided in the housing; an imaging optical system including a bending optical system having two reflecting surfaces which bend an optical path of the imaging optical system, an incident surface of the bending optical system being exposed outwardly from the housing; an image sensor installed in the housing and includes an imaging surface which receives light reflected by one of the reflecting surfaces positioned on an exit side of the imaging optical system; a circuit board which closes at least part of the opening and to which the image sensor is fixedly connected; and a cover fixedly fitted to the housing so as to close the opening and press the circuit board toward the image sensor so that the image sensor or the circuit board comes in contact with the positioning portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an imaging unit having an imagingoptical system and an image sensor that captures light emanating from aphotographic object which is passed through the imaging optical system.The imaging optical system and the image sensor are accommodated in ahousing of the imaging unit.

2. Description of the Related Art

In recent years, mobile electronic devices which are designed mainly fortaking still/moving photographic images, such as digital cameras(still-video cameras) and digital camcorders (motion-video cameras), andother mobile electronic devices which are designed to have thecapability of taking such photographic images as a subsidiary function,such as mobile phones equipped with a camera and personal digitalassistants (PDAs) equipped with a camera, have become widespread. Inthese types of mobile electronic devices, it is common to provide themobile electronic device therein with an imaging unit which isstructured such that an image sensor and a photographing optical systemfor leading light emanating from a photographic object (object to bephotographed) to the image sensor are accommodated in a hollow housingof the imaging unit. Additionally, in recent years, the downsizing(slimming down) of the mobile electronic devices has further progressed,so that the demand to also slim down the imaging unit has becomestronger.

Japanese Unexamined Patent Publication No. 2008-242446 discloses anexample of a conventional imaging unit. This imaging unit is providedwith a box-shaped housing, an imaging optical system (including anincident-side prism, an exit-side prism and lens groups positionedbetween the incident-side prism and the exit-side prism), an imagesensor (image pickup device) and a substrate (circuit board). Thehousing has an opening on a surface on one of the opposite sides thereofin the direction of the thickness of the housing. The imaging opticalsystem and the image sensor are housed in the housing, and the substrateis fixed to the housing so as to close the opening of the housing, andthe image sensor is fixedly connected to an inner surface of thesubstrate. The traveling direction of light emanating from aphotographic object which is incident on the incident-side prism (whichserves as an incident portion of the imaging optical system) changes(i.e., is reflected) at an angle of 90 degrees by the incident-sideprism, and thereafter passes through the aforementioned lens groups tobe incident on the exit-side prism. Thereupon, the traveling directionof the light incident on the exit-side prism again changes (i.e., isreflected) at an angle of 90 degrees by the exit-side prism to bereceived (captured) by the imaging surface (photosensitive surface) ofthe image sensor.

This imaging unit uses the aforementioned substrate, which supports theimage sensor, as a cover for closing the aforementioned opening of thehousing, thus making it possible to reduce the thickness of the entireimaging unit as compared with the case where the substrate is includedinside a housing the entire surface thereof being closed.

If the thickness of the substrate in the aforementioned JapaneseUnexamined Patent Publication No. 2008-242446 is reduced, the mechanicalstrength of the substrate deteriorates, which causes the substrate tobend to thereby displace the position of the imaging surface from theoriginal position thereof if an external force is exerted thereon orvibrations occur in a mobile electronic device which incorporates theimaging unit. Therefore, the substrate needs to be thick, to a certainextent, in the imaging unit disclosed in the aforementioned JapaneseUnexamined Patent Publication No. 2008-242446; however, an increase inthickness of the substrate causes an increase in thickness of theimaging unit.

SUMMARY OF THE INVENTION

The present invention provides an imaging unit having a structure so asto be capable of securely positioning the image sensor while achieving areduction in thickness of the entire imaging unit without incurring anincrease in the number of components of the imaging unit.

According to an aspect of the present invention, an imaging unit isprovided, including a housing having an opening; a positioning portionprovided in the housing; an imaging optical system including first andsecond reflecting surfaces, provided on an incident side and an exitside of the imaging optical system, respectively, the first and secondreflecting surfaces bending an optical path of the imaging opticalsystem, wherein an incident surface of the imaging optical system isexposed outwardly from the housing; an image sensor which is installedin the housing and includes an imaging surface which receives lightreflected by the second reflecting surface; a circuit board which closesat least part of the opening and to which the image sensor is fixedlyconnected; and a cover, made of metal, which is fixedly fitted to thehousing so as to close the opening and press the circuit board towardthe image sensor so that one of the image sensor and the circuit boardcomes in contact with the positioning portion.

It is desirable for a traveling direction of light which travels fromthe incident surface toward the first reflecting surface to be oppositeto a traveling direction of light reflected by the second reflectingsurface.

It is desirable for the cover to include at least one pressure leafwhich is resiliently deformable and presses the circuit board toward theimage sensor.

It is desirable for the opening to be formed on one of opposite sides ofthe housing in the direction of thickness of the housing, for the imagesensor to include a flat cover glass which covers the imaging surface,and for the positioning portion to include at least one flat positioningsurface which is orthogonal to a direction of thickness of the housingand with which the cover glass is in surface contact.

It is desirable for the positioning portion to include a prism mountingrecess which is open to the opening side; and at least one positioningprojection formed around the prism mounting recess, wherein thepositioning projection projects toward the opening and includes the flatpositioning surface at an end surface of the positioning projection. Theimaging optical system includes a prism which is installed in the prismmounting recess and reflects incident light toward the imaging surface,and the imaging unit further includes a packing made of an elasticmaterial which includes an exposing hole through which the imagingsurface is exposed toward the prism side and a through-hole throughwhich the positioning projection passes, the packing being held betweenthe positioning portion and the image sensor.

It is desirable for the housing to include at least two engagingprojections formed on two side surfaces positioned on opposite sides ofthe housing. The cover includes corresponding at least two resilientengaging lugs having engaging holes in which the at least two engagingprojections are disengageably engageable.

It is desirable for the imaging optical system to include a lens groupthat is movable along an optical path that is bent by the firstreflecting surface. The opening is formed entirely in the one surface ofthe housing. The movable lens group and the image sensor are installedin an internal space of the housing.

It is desirable for the positioning portion to be formed integral withthe housing.

According to the present invention, the image sensor can be correctlypositioned with respect to the housing via the positioning portion ofthe housing and the cover since the circuit board is pressed toward theimage sensor by the cover so that the image sensor or the circuit boardcomes in contact with the positioning portion that is formed inside thehousing if the opening of the housing is closed by the cover.

The cover is made of metal, thus showing an appropriate mechanicalstrength though even if the thickness of the cover is reduced.Therefore, even if an external force is exerted on the imaging unit orvibrations occur in the imaging unit when the thickness of the entireimaging unit is reduced by reducing the thickness of the circuit boardand the cover, the image sensor (the imaging surface thereof) can beheld at a predetermined position.

Moreover, the positioning of the image sensor with respect to thehousing does not cause an increase in the number of components becausesuch positioning is carried out using the cover.

The present disclosure relates to subject matter contained in JapanesePatent Applications Nos. 2010-219530 (filed on Sep. 29, 2010),2010-230839 (filed on Oct. 13, 2010), 2010-232558 (filed on Oct. 15,2010) and 2011-021974 (filed on Feb. 3, 2011) which are expresslyincorporated herein by reference in their entireties.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described below in detail with referenceto the accompanying drawings in which:

FIG. 1 is a front perspective view of an embodiment of an imaging unitaccording to the present invention, viewed obliquely from above;

FIG. 2 is a front exploded perspective view of the imaging unit, viewedobliquely from above;

FIG. 3 is a front elevational view of the imaging unit;

FIG. 4 is a front elevational view of the imaging unit with a cover anda circuit board removed when an imaging optical system is set at thetelephoto extremity;

FIG. 5 is a cross sectional view taken along the line V-V shown in FIG.1 when the imaging optical system is set at the telephoto extremity;

FIG. 6 is a view similar to that of FIG. 4, showing the imaging unitwith the cover and the circuit board removed when the imaging opticalsystem is set at the wide-angle extremity;

FIG. 7 is a perspective view of a second lens group frame, a first lightshield frame and peripheral parts;

FIG. 8 is a perspective view of a third lens group frame, a second lightshield frame and peripheral parts;

FIG. 9 is a perspective view of the cover in a modified embodiment ofthe imaging unit;

FIG. 10 is an exploded perspective view of another modified embodimentof the imaging unit; and

FIG. 11 is a view similar to that of FIG. 5, showing yet anothermodified embodiment of the imaging unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following descriptions, forward and rearward directions, leftwardand rightward directions, and upward and downward directions aredetermined with reference to the directions of the double-headed arrowsshown in the drawings.

As shown in FIGS. 1 and 2, the imaging unit 10 is provided with a bodymodule 15, a board module 65 and a cover 76 constitute the majorcomponents of the imaging unit 10.

The body module 15 is provided with a housing (casing) 16 made ofsynthetic resin. The housing 16 is provided at the front left endthereof with a mounting recess 17 formed into the shape of a letter D incross section. In addition, the housing 16 is provided, on the frontthereof except this front left end (on the substantially entire frontpart of the housing 16), with a substantially rectangular accommodatingrecess (opening) 18. The housing 16 is provided between the mountingrecess 17 and the accommodating recess 18 with a partition wall 19. Thehousing 16 is provided at a center of the partition wall 19 with acommunication hole (through-hole) 20 (see FIGS. 4 through 6) via whichthe mounting recess 17 and the accommodating recess 18 arecommunicatively connected with each other. The housing 16 is provided,in the accommodating recess 18 at the right end thereof, with apositioning portion 22 having a substantially rectangular shape, in afront view, which projects forward from the base of the accommodatingrecess 18 (i.e., from a front surface of the base surface in theaccommodating recess 18). The positioning portion 22 is provided withthree positioning projections 23 (spacers) which project forward, andthe front end surfaces of the three positioning projections 23 areformed as flat positioning surfaces 24 which lie in a common planeorthogonal to the forward/rearward direction (i.e., the direction of thethickness of the housing 16). In addition, the housing 16 is provided inthe positioning portion 22 with a prism mounting recess 25 which is openat the front and left sides. The positioning portion 22 is provided onthe left side thereof with a pair of (upper and lower) limit projections(light shield frame position limit portions) 26 which project leftward(see FIG. 6), and the left end surface of the pair of limit projections26 are formed as light shield frame position limit surfaces 26 a whichare flat surfaces lying in a common plane orthogonal to theleftward/rightward direction (i.e., in a common plane orthogonal to thelongitudinal direction of the housing 16). The housing 16 is provided,around the front edge of the inner peripheral surface of theaccommodating recess 18, with a board support surface 27 which ispositioned behind the frontmost end of the housing 16 and lies in aplane orthogonal to the forward/rearward direction, and is furtherprovided on the board support surface 27 with two lock projections 28which project forward from the board support surface 27. The housing 16is provided, at the front end of the center of the upper surface of thehousing 16, with a first engaging recess 30 which is recessed downwardfrom the upper surface (periphery) of the housing 16. The housing 16 isalso provided, at the front end of the upper surface of the housing 16on the left-hand side of the first engaging recess 30, with a secondengaging recess 31 which is recessed downward from the upper surface(periphery) of the housing 16 by the same amount as the first engagingrecess 30 and is wider than the first engaging recess 30. The housing 16is provided in the second engaging recess 31 with an engaging projection32. The housing 16 is also provided on the lower surface thereof with afirst engaging recess 30, a second engaging recess 31 and an engagingprojection 32 which have the same configurations as those provided onthe upper surface of the housing 16. The positional relationship betweenthe first engaging recess 30, the second engaging recess 31 and theengaging projection 32 which are formed on the lower surface of housing16 is identical to the positional relationship between the firstengaging recess 30, the second engaging recess 31 and the engagingprojection 32 which are formed on the upper surface of housing 16;however, the positions of the first engaging recess 30, the secondengaging recess 31 and the engaging projection 32 which are formed onthe lower surface of the housing 16 in the leftward/rightward directionare all shifted to the right with respect to those formed on the uppersurface of the housing 16. Additionally, the housing 16 is provided onthe right side thereof with a pair of (upper and lower) engagingprojections 34.

As shown in FIGS. 4 through 6, the body module 15 is provided in themounting recess 17 with a first prism (incident-side prism/incident-side reflecting surface) LP1 that is fit-engaged in themounting recess 17 and fixed thereto. The first prism LP1 is providedwith an incident surface LP1-a which is orthogonal to theforward/rearward direction and an exit surface LP1-b which is orthogonalto the leftward/rightward direction. The body module 15 is provided witha lens (lens element) L1 which is fitted into the front end of themounting recess 17 and fixed thereto. The lens L1 is substantially thesame in cross sectional shape as the mounting recess 17, and the opticalaxis of the lens L1 extends in the forward/rearward direction. The frontsurface of the lens L1 is exposed to the front of the imaging unit 10,and the rear surface of the lens L1 and the incident surface LP1-a faceeach other in the forward/rearward direction. As shown in FIGS. 2 and 5,the body module 15 is provided with two lenses (lens elements) L2 and L3which are fixedly fitted into the communication hole 20 to face the exitsurface LP1-b of the first prism LP1 in the leftward/rightwarddirection. The lens L1, the first prism LP1, the lens L2 and the lens L3are optical elements of a first lens group LG1 provided in the bodymodule 15.

The body module 15 is provided in the prism mounting recess 25 with asecond prism (exit-side prism/exit-side reflecting surface) LP2 that isfit-engaged in the prism mounting recess 25 and fixed thereto. Thesecond prism LP2 has an incident surface LP2-a which is orthogonal tothe leftward/rightward direction and an exit surface LP2-b which isorthogonal to the forward/rearward direction. The incident surface LP2-afaces the exit surface LP1-b in the leftward/rightward direction.

The body module 15 is provided with a first rod (cylindrical rod) 36 anda second rod (cylindrical rod) 37 which are made of metal and extendlinearly in the leftward/rightward direction. The first rod 36 and thesecond rod 37 are each fixed at both ends thereof to an inner surface ofthe right side wall of the housing 16 and the partition wall 19 so thatthe left ends of the first rod 36 and the second rod 37 are aligned inthe upward/downward direction and so that the right ends of the firstrod 36 and the second rod 37 are aligned in the upward/downwarddirection.

The body module 15 is provided with a second lens group frame 39 made ofsynthetic resin. An insertion hole 40 in which the first rod 36 isinserted is formed through the upper part of the second lens group frame39, and a rotation prevention groove 41 in which the second rod 37 isengaged is formed in the lower end of the second lens group frame 39.The second lens group frame 39 is prevented from rotating about thefirst rod 36 by the engagement of the rotation prevention groove 41 withthe second rod 37, and accordingly, the second lens group frame 39 canslide on and along the first rod 36 and the second rod 37 in theleftward/rightward direction. The body module 15 is provided with asecond lens group (movable lens group/first movable lens group) LG2configured of two lenses (lens elements) L4 and L5 which face the exitsurface LP1-b of the first prism LP1 and the incident surface LP2-a ofthe second prism LP2 in the leftward/rightward direction, respectively.The second lens group LG2 is fixedly fitted into a lens holding holewhich is formed through the second lens group frame 39 in theleftward/rightward direction. A light shielding sheet 43 which isprovided at a center thereof with a light-bundle limiting aperture 43 ais fixed to the right side surface of the second lens group frame 39 sothat the center of the light-bundle limiting aperture 43 a is positionedcoaxially with the optical axis of the lenses L4 and L5. In addition, anut holding hole 42, both ends of which in the leftward/rightwarddirection are formed as open ends, is formed at the upper end of thesecond lens group frame 39, and a driven nut (upper driven nut) 44through which a female screw hole with the axis thereof extending in theleftward/rightward direction is formed is fixedly fitted into the nutholding hole 42 (the end of the nut holding hole 42 at the first rod 36constitutes a rotation stop for the upper driven nut 44). The bodymodule 15 is provided with a first motor M1 configured of a steppingmotor which is fixed to the housing 16 in the upper part of theaccommodating recess 18. The first motor M1 is provided with a rotarydrive shaft M1 a which extends linearly leftwards, and a male screwthread formed on the rotary drive shaft M1 a in the vicinity of the end(left end with respect to FIG. 4) thereof is screw-engaged with theaforementioned female screw hole of the upper driven nut 44.Accordingly, forward and reverse rotations of the rotary drive shaft M1a that are caused by forward and reverse rotations of the first motor M1cause the second lens group frame 39 (the lenses L4 and L5) to movelinearly between the telephoto extremity position (shown in FIGS. 4 and5) and the wide-angle extremity position (shown in FIG. 6) in theleftward/rightward direction along the first rod 36 and the second rod37.

In addition, the body module 15 is provided with a third lens groupframe (second movable lens frame) 47 made of synthetic resin. Aninsertion hole 48 in which the second rod 37 is inserted is formedthrough the lower part of the third lens group frame 47, and a rotationprevention groove 49 in which the first rod 36 is engaged is formed inthe upper end of the third lens group frame 47. Accordingly, the thirdlens group frame 47 can slide on and along the first rod 36 and thesecond rod 37 in the leftward/rightward direction (while being preventedfrom rotating about the second rod 37). The body module 15 is providedwith a third lens group (movable lens group/second movable lens group)LG3 configured of a lens (lens element) L6 and the optical axis thereofis coaxial with the optical axis of the second lens group LG2. The thirdlens group LG3 is fixedly fitted into a lens holding hole which isformed through the third lens group frame 47 in the leftward/rightwarddirection. A nut holding hole 50, both ends of which in theleftward/rightward direction are formed as open ends, is formed at thelower end of the third lens group frame 47, and a driven nut (lowerdriven nut) 44, through which a female screw hole with the axis thereofextending in the leftward/rightward direction is formed, is fixedlyfitted into the nut holding hole 50 (the end of the nut holding hole 50at the second rod 37 constitutes a rotation stop for the lower drivennut 44). The body module 15 is provided with a second motor M2 which isidentical in specifications to the first motor M1 and fixed to thehousing 16 in the lower part of the accommodating recess 18. The secondmotor M2 is provided with a rotary drive shaft M2 a (identical inspecifications to the rotary drive shaft M1 a), and a male screw threadformed on the rotary drive shaft M2 a in the vicinity of the end (leftend with respect to FIG. 4) is screw-engaged with the aforementionedfemale screw hole of the lower driven nut 44. Therefore, forward andreverse rotations of the rotary drive shaft M2 a that are caused byforward and reverse rotations of the second motor M2 cause the thirdlens group frame 47 (the third lens group L3) to move linearly betweenthe telephoto extremity position (shown in FIGS. 4 and 5) and thewide-angle extremity position (shown in FIG. 6) in theleftward/rightward direction along the first rod 36 and the second rod37.

The first lens group LG1 (L1, LP1, L2 and L3), the second lens group LG2(L4 and L5), the third lens group LG3 (L6) and the second prism LP2 thathave been described above are optical elements of an imaging opticalsystem (bending optical system). A zooming operation is performed bymoving the second lens group LG2 (the lenses L4 and L5) and the thirdlens group LG3 (the lens L6) along the first rod 36 and the second rod37, and a focusing operation is performed by moving only the third lensgroup LG3 along the first rod 36 and the second rod 37.

It should be noted that the housing 16, the first rod 36, the second rod37, the imaging optical system, the first motor M1 and the second motorM2 are components of the body module 15.

The body module 15 is provided, in the vicinity of the first rod 36 inthe accommodating recess 18, with a columnar guide bar (upper guide bar)52 made of metal which extends parallel to the first rod 36, the secondrod 37 and an optical axis A of the lenses L2 through L6. The left endof the guide bar 52 is fixed to the second lens group frame 39 in thevicinity of the upper end thereof. A metal slidable cylinder (upperslidable cylinder) 53 is fitted on the guide bar 52 to be freelyslidable thereon. The guide bar 52 is integrally provided at the rightend thereof with a stopper 52 a that is disk-shaped, the diameter ofwhich is greater than the inner diameter of the slidable cylinder 53. Acompression coil spring (biaser) S1 is installed around the first rod 36and positioned between the second lens group frame 39 and the slidablecylinder 53. The left end and the right end of the compression coilspring S1 are fixed to the second lens group frame 39 and the slidablecylinder 53, respectively. When no external force is applied to theslidable cylinder 53 (when the slidable cylinder 53 is at the telephotoextremity position thereof), the compression coil spring S1 is in a freestate in which the slidable cylinder 53 is positioned between the rightend of the compression coil spring S1 and the stopper 52 a (a space isprovided between the slidable cylinder 53 and the stopper 52 a).

The body module 15 is provided with a first light shield frame 54 madeof a lightproof material, the upper end of which is fixed to theslidable cylinder 53. The first light shield frame 54 is a planar memberorthogonal to the axis of the guide bar 52. The first light shield frame54 is provided at a center thereof with a light-bundle limiting aperture54 a in the shape of a rectangle. The first light shield frame 54 isprovided at the upper end thereof with a fixing hole 54 b which isfixedly engaged with the slidable cylinder 53, and the first lightshield frame 54 is provided at the lower end thereof with a rotationprevention groove 54 c in which the second rod 37 is engaged. Movementof the slidable cylinder 53 together with the guide bar 52 and thesecond lens group frame 39 in the leftward/rightward direction causesthe first light shield frame 54 to slide on and along the second rod 37in the leftward/rightward direction.

The body module 15 is provided, in the vicinity of the second rod 37 inthe accommodating recess 18, with a columnar guide bar (lower guide bar)58 (see FIGS. 1 and 8) which is identical in specifications to the upperguide bar 52 and extends parallel to the guide bar 52. The left end ofthe guide bar 58 is fixed to the third lens group frame 47 in thevicinity of the lower end thereof. A metal slidable cylinder (lowerslidable cylinder) 53 (identical in specifications to the upper slidablecylinder 53) is fitted on the guide bar 58 to be freely slidablethereon. The guide bar 58 is integrally provided at the right endthereof with a stopper 58 a that is disk-shaped, the diameter of whichis greater than the inner diameter of the lower slidable cylinder 53. Acompression coil spring (biaser) S2 is installed on the second rod 37and positioned between the third lens group frame 47 and the lowerslidable cylinder 53 in a compressed state (resiliently deformed state).The compression coil spring S2 provides a biasing force so that thelower slidable cylinder 53 is biased to move rightward, and accordingly,the lower slidable cylinder 53 abuts the stopper 58 a when no leftwardexternal force is applied to the lower slidable cylinder 53.

The body module 15 is provided with a second light shield frame 59 whichis positioned between the first light shield frame 54 and the secondprism LP2 and the lower end of which is fixed to the lower slidablecylinder 53 that is supported by the guide bar 58. The second lightshield frame 59 is made of a lightproof material and configured from aplanar member orthogonal to the axis of the guide bar 58. The secondlight shield frame 59 is provided at a center thereof with alight-bundle limiting aperture 59 a in the shape of a rectangle. Thesecond light shield frame 59 is provided at the lower end thereof with afixing hole 59 b which is fixedly engaged with the lower slidablecylinder 53, and the second light shield frame 59 is provided at theupper end thereof with a rotation prevention groove 59 c in which thefirst rod 36 is engaged. Movement of the lower slidable cylinder 53,which is supported by the guide bar 58, together with the guide bar 58and the third lens group frame 47 in the leftward/rightward directioncauses the second light shield frame 59 to slide on and along the firstrod 36 in the leftward/rightward direction.

Among the above described components, the pair of limit projections 26,the second rod 37, the second lens group frame 39, the guide bar 52, theupper slidable cylinder 53 and the compression coil spring S1 arecomponents of a light-shield-frame position adjustment mechanism for thefirst light shield frame 54. In addition, the pair of limit projections26, the first rod 36, the third lens group frame 47, the lower slidablecylinder 53, the guide bar 58 and the compression coil spring S2 arecomponents of a light-shield-frame position adjustment mechanism for thesecond light shield frame 59.

The board module 65 is provided with a circuit board 66. The circuitboard 66 has substantially the same front shape as that shape of theaccommodating recess 18 and is configured from a flat plate orthogonalto the forward/rearward direction. The circuit board 66 is provided onthe rear surface thereof with a printed circuit (not shown), and twocircular holes 67 are formed through two diagonally opposite corners ofthe circuit board 66, respectively.

The board module 65 is provided with an image sensor (image pickupdevice) 69 (see FIGS. 1 and 5) which is fixed at the right end of therear surface of the circuit board 66. A plurality of terminals (notshown) of the image sensor 69 are fixedly connected to theaforementioned printed circuit by soldering. The image sensor 69 isprovided on the rear thereof with an imaging surface (not shown)orthogonal to the forward/rearward direction. In addition, the imagesensor 69 is provided, on the incident surface (the rear surface in thedrawings), with a cover glass 70 which is made of a flat glass plate andfixedly installed so as to cover the entire imaging surface of the imagesensor 69.

A rear surface (rear end) of the image sensor 69 is covered with apacking (fixer) 72 made of an elastic material such as rubber which isopen at the front and left sides. The packing 72 is provided with anexposing hole (through-hole) 73 through which the entire imaging surfaceof the image sensor 69 is rearwardly exposed, and is further provided onthe right-hand side of the exposing hole 73, with a through-hole 74.

The circuit board 66, the image sensor 69 and the packing 72 that havebeen described above are components of the board module 65.

The cover (casing) 76 is a press-molded sheet metal product and isintegrally provided with a base 77, two (upper and lower) short engaginglugs 78, two (upper and lower) long engaging lugs (resilient engaginglug) 79 and a pair of (upper and lower) side engaging lugs (resilientengaging lugs) 81. The base 77 is formed as a planar member orthogonalto the forward/rearward direction. The upper short engaging lug 78 andthe upper long engaging lug 79 extend rearward from the upper edge ofthe base 77, and the lower short engaging lug 78 and the lower longengaging lug 79 extend rearward from the lower edge of the base 77. Thepair of side engaging lugs 81 extend rearward from the right edge of thebase 77. Each side engaging lug 81 is in shape of a letter T as viewedfrom a side thereof. The base 77 is slightly greater in size(dimensions) than the circuit board 66 and has a substantiallyrectangular shape with a size capable of closing the front opening(defined by the accommodating recess 18) of the housing 16 (this size issubstantially the same as or greater than the front opening of thehousing 16). The base 77 is provided with three pressure leaves 84, 85and 86 each of which is resiliently deformable in the forward/rearwarddirection.

The pressure leaves 84, 85 and 86 are provided with pressure projections84 a, 85 a and 86 a, respectively, which project rearwardly (portions ofthe front surfaces of the pressure leaves 84, 85 and 86 whichrespectively correspond to the pressure projections 84 a, 85 a and 86 aare dent (recessed) rearward). The pressure leaves 84, 85 and 86 in afree state lie in a plane in which the other part of the base 77 lies.

An engaging hole 80 and an engaging hole 82 are formed through each longengaging lug 79 and each side engaging lug 81, respectively.

To install the board module 65 and the cover 76 to the body module 15,firstly the front opening of the accommodating recess 18 is closed bythe circuit board 66 so that the outer edge of the rear surface of thecircuit board 66 comes into surface contact with the board supportsurface 27 while the two circular holes 67 of the circuit board 66 arebrought into engagement with the two lock projections 28 (thereupon, thefront surface of the circuit board 66 and the front surface of thehousing 16 substantially lie in a common plane). Thereupon, as shown inFIG. 5, the three positioning projections 23 of the housing 16 forwardlypass through the exposing hole 73 and the through-hole 74 of the packing72 so that the flat positioning surfaces 24 of the three positioningprojections 23 come in surface contact with a flat rear surface of thecover glass 70 (at the outer periphery of a rear surface portionimmediately behind the imaging surface of the image sensor 69). Inaddition, the imaging surface of the image sensor 69 faces the exitsurface LP2-b of the second prism LP2 in the forward/rearward directionthrough the exposing hole 73. Additionally, a rear surface of thepacking 72 comes in contact with the front surface of the positioningportion 22.

Subsequently, the base 77 fully covers, from the front, a portion of thefront of the housing 16 from the partition wall 19 rightward to fix thecover 76 to the housing 16 by respectively engaging the upper and lowershort engaging lugs 78 with the first engaging recesses 30, respectivelyengaging the upper and lower engaging holes 80 of the upper and lowerlong engaging lugs 79 with the upper and lower engaging projections 32,and respectively engaging the engaging holes 82 of the upper and lowerside engaging lugs 81 with the upper and lower engaging projections 34.

Upon the imaging unit 10 being assembled in the above described manner,the circuit board 66 and the image sensor 69 are pressed rearward due tothe pressure projections 84 a, 85 a and 86 a of the pressure leaves 84,85 and 86 coming in contact with a right-hand side portion of the frontsurface of the circuit board 66 so that a pressing force (biasing force)in the rearward direction acts on the front side of the circuit board 66from the pressure leaves 84, 85 and 86 (via the pressure projections 84a, 85 a and 86 a) that are slightly resiliently deformed forwardly.Thereupon, an integral combination of the circuit board 66 and the imagesensor 69 is held from the front and the rear sides thereof between theflat positioning surfaces 24 of the three positioning projections 23 andthe pressure projections 84 a, 85 a and 86 a of the cover 76, andaccordingly, the circuit board 66 and the image sensor 69 are preciselypositioned with respect to the housing 16 and the second prism LP2 inthe forward/rearward direction by the three positioning projections 23of the housing 16 and the pressure projections 84 a, 85 a and 86 a ofthe cover 76.

Since the cover 76 is made of metal, each of the base 77 and thepressure leaves 84, 85 and 86 exhibits an appropriate mechanicalstrength even if the thickness of the cover 76 is small. Therefore, evenif an external force is exerted on the imaging unit 10 or vibrationsoccur in the imaging unit 10 when it is attempted to reduce thethickness of the entire imaging unit 10 by reducing the thickness thecircuit board 66 and the cover 76, the position of the image sensor 69(the imaging surface thereof) in the forward/rearward direction is heldat a predetermined design position.

Moreover, the positioning of the image sensor 69 with respect to thehousing 16 and the second prism LP2 does not cause an increase in thenumber of components because such positioning is carried out using thecover 76.

If the imaging unit 10 is directed toward an object located in front ofthe imaging unit 10, light reflected by the object (light emanating froma photographic object) enters the first prism LP1 through the incidentsurface LP1-a after passing through the lens L1 and is reflected at anangle of 90 degrees by an inner surface of the first prism LP1 to traveltoward the exit surface LP-1 b. Subsequently, the reflected light thatemerges from the exit surface LP1-b enters the second prism LP2 from theincident surface LP2-a after passing through the lenses L2 through L6,the light-bundle limiting aperture 54 a of the first light shield frame54 and the light-bundle limiting aperture 59 a of the second lightshield frame 59, and is reflected at an angle of 90 degrees by an innersurface of the second prism LP2 to travel toward the exit surface LP-2b. Subsequently, the reflected light that emerges from the exit surfaceLP2-b is captured (received) by the aforementioned imaging surface ofthe image sensor 69 after passing through the exposing hole 73 and thecover glass 70.

Even if an external force is exerted on the imaging unit 10 orvibrations occur in the imaging unit 10 as described above, the positionof the image sensor 69 (the imaging surface thereof) in theforward/rearward direction is held at a predetermined design positionwith precision, and accordingly, a sharp object image with no blur canbe captured by the image sensor 69 even if an external force is exertedon the imaging unit 10 or vibrations occur in the imaging unit 10 asdescribed above.

Additionally, if the above described imaging optical system is driven toperform a zooming operation and a focusing operation by moving thesecond lens group LG2 (the lenses L4 and L5) and the third lens groupLG3 (the lens L6) along the first rod 36 and the second rod 37 with thefirst motor M1 and the second motor M2, an image capturing operation ina state where the imaging optical system is zoomed and focused on aphotographic object image becomes possible.

Although the present invention has been described based on the aboveillustrated embodiment, making various modifications to the aboveillustrated embodiment is possible.

For instance, the pressure leaves 84, 85 and 86 can be made to beinclined rearwardly with respect to the base 77 when the pressure leaves84, 85 and 86 are in free state so that the free ends thereof arepositioned behind the peripheral portions that surround the pressureleaves 84, 85 and 86, respectively, on the front surface of the base 77.This structure makes it possible to increase the aforementioned pressingforce that is applied to the circuit board 66 from the pressure leaves84, 85 and 86 (the pressure projections 84 a, 85 a and 86 a) when thecover 76 is fixed to the housing 16.

In the case where the pressure leaves 84, 85 and 86 are made to beinclined rearwardly, the pressure projections 84 a, 85 a and 86 a can beomitted.

The number of the pressure leaves (84, 85 and 86) of the cover 76 can beone or two, or more than three.

Furthermore, the shapes of the pressure leaves 84, 85 and 86 can bemodified, e.g., as those formed on a cover 76′ shown in FIG. 9.

Alternatively, the pressure leaves 84, 85 and 86 can be omitted from thebase 77 by forming projections corresponding to the pressure projections84 a, 85 a and 86 a on the back of the base 77.

Additionally, a rear surface of the circuit board 66 can be made tocontact the three positioning projections 23 (the flat positioningsurfaces 24 thereof) instead of a rear surface of the image sensor 69.

It is possible to make the image sensor 69 or the circuit board 66 abuta front surface (positioning surface) of the positioning portion 22 withthe three positioning projections 23 omitted from the positioningportion 22.

It is possible to mold the positioning portion 22 (the three positioningprojections 23) as a separate member from the housing 16 and to fix thepositioning portion 22 to the housing 16 after molding the positioningportion 22.

Additionally, the dimensions of the circuit board 66 can be determinedso as only to close part of the front opening of the accommodatingrecess 18.

Additionally, as shown in FIG. 10, it is possible for the body module 15to be configured of a first lens group unit 1 and a body unit 2 that areindependent of each other and for the housing (which corresponds to thehousing 16) of the body module 15 be configured of two components (aholder 3 and a main housing 7).

The first lens group unit 1 is provided with a holder 3 formed as asynthetic-resin molded product. The holder 3 is provided at the left endthereof with a pair of (upper and lower) lugs 4, each of which has athrough-hole 5. A prism accommodating space which is open at the frontand right sides is formed in the holder 3. The holder 3 is provided atthe front opening of the prism accommodating space with a front lensholding hole 6 which is open at the front and at a left portion thereof,and is provided at the right opening of the prism accommodating spacewith a right lens holding hole. The first prism LP1 is fitted into theprism accommodating hole to be fixed therein, and the lens L1 is fittedinto the front lens holding hole 6 to be fixed therein. In addition, thelenses L2 and L3 are fitted into the right lens holding hole to be fixedtherein.

The main housing 7 of the body unit 2 is identical in structure to thehousing 16 from which a left end portion thereof (which corresponds tothe holder 3) is removed, and is provided at the left end of the mainhousing 7 with an installation recess 8. In addition, the samecomponents as those installed in the accommodating recess 18 of thehousing 16 are installed in the accommodating recess 18 of the mainhousing 7, and the front of the main housing 7 is covered with the cover76.

The first lens group unit 1 and the body unit 2 are fixed together asone unit by inserting from the left side a pair of set screws B into theupper and lower through-holes 5 of the holder 3 and screwing the malethread portions of the pair of set screws B into a pair of female screwholes (not shown) formed in upper and lower left end surfaces of themain housing 7 with a portion of the holder 3 which is positioned on theright-hand side of the pair of lugs 4 being fitted into the installationrecess 8 and with a pair of (upper and lower) spacers S held between theupper and lower lugs 4 of the holder 3 and the upper and lower left endsurfaces of the main housing 7 (that are the left end surfaces of a pairof projections of the main housing 7 which are formed on the verticallyopposite sides of the installation recess 8).

Upon the first lens group unit 1 and the body unit 2 being fixedtogether as one unit, the right end of the holder 3 (in which the rightlens holding hole is formed) is fitted into the communication hole 20(not shown in FIG. 10) of the partition wall 19 of the main housing 7,and the optical axis A of the lenses L2 and L3 coincides with theoptical axis of the second lens group LG2 and the third lens group LG3.

In addition, the technical principle of “the formation of an opening inan entire surface of the housing” claimed in the claims of the presentinvention does not limit the size of the opening of the housing to thatdisclosed in the above illustrated embodiment; namely, such a technicalprinciple is a concept including the formation of the opening, the sizeof which relative to the housing is slightly smaller or greater thanthat disclosed in the above illustrated embodiment.

Additionally, the direction of the optical path passing through theimaging optical system (the first lens group LG1, the second lens groupLG2, the third lens group LG3 and the second prism LP2) can be changedby making the lens L1 exposed toward the opposite side of the imagingunit 10 from the cover 76 side in the forward/rearward direction bymodifying the shape of a housing 16′ as shown in FIG. 11 (a modificationin which a portion of the housing which corresponds to the holder 3shown in the modified embodiment in FIG. 10 is inverted in theforward/rearward direction.

Additionally, each of the first prism LP1 and the second prism LP2 canbe replaced by a mirror.

Obvious changes may be made in the specific embodiments of the presentinvention described herein, such modifications being within the spiritand scope of the invention claimed. It is indicated that all mattercontained herein is illustrative and does not limit the scope of thepresent invention.

1. An imaging unit comprising: a housing having an opening; apositioning portion provided in said housing; an imaging optical systemincluding first and second reflecting surfaces, provided on an incidentside and an exit side of said imaging optical system, respectively, saidfirst and second reflecting surfaces bending an optical path of saidimaging optical system, wherein an incident surface of said imagingoptical system is exposed outwardly from said housing; an image sensorwhich is installed in said housing and includes an imaging surface whichreceives light reflected by said second reflecting surface; a circuitboard which closes at least part of said opening and to which said imagesensor is fixedly connected; and a cover, made of metal, which isfixedly fitted to said housing so as to close said opening and presssaid circuit board toward said image sensor so that one of said imagesensor and said circuit board comes in contact with said positioningportion.
 2. The imaging unit according to claim 1, wherein a travelingdirection of light which travels from said incident surface toward saidfirst reflecting surface is opposite to a traveling direction of lightreflected by said second reflecting surface.
 3. The imaging unitaccording to claim 1, wherein said cover comprises at least one pressureleaf which is resiliently deformable and presses said circuit boardtoward said image sensor.
 4. The imaging unit according to claim 1,wherein said opening is formed on one of opposite sides of said housingin the direction of thickness of said housing, wherein said image sensorcomprises a flat cover glass which covers said imaging surface, andwherein said positioning portion comprises at least one flat positioningsurface which is orthogonal to said direction of thickness of saidhousing and with which said cover glass is in surface contact.
 5. Theimaging unit according to claim 4, wherein said positioning portioncomprises: a prism mounting recess which is open to said opening side;and at least one positioning projection formed around said prismmounting recess, wherein said positioning projection projects towardsaid opening and includes said flat positioning surface at an endsurface of said positioning projection, wherein said imaging opticalsystem comprises a prism which is installed in said prism mountingrecess and reflects incident light toward said imaging surface, andwherein said imaging unit further comprises a packing made of an elasticmaterial which includes an exposing hole through which said imagingsurface is exposed toward said prism side and a through-hole throughwhich said positioning projection passes, said packing being heldbetween said positioning portion and said image sensor.
 6. The imagingunit according to claim 1, wherein said housing comprises at least twoengaging projections formed on two side surfaces positioned on oppositesides of said housing, and wherein said cover comprises corresponding atleast two resilient engaging lugs having engaging holes in which said atleast two engaging projections are disengageably engageable.
 7. Theimaging unit according to claim 1, wherein said imaging optical systemcomprises a lens group that is movable along an optical path that isbent by said first reflecting surface, wherein said opening is formedentirely in one surface of said housing, and wherein said movable lensgroup and said image sensor are installed in an internal space of saidhousing.
 8. The imaging unit according to claim 1, wherein saidpositioning portion is formed integral with said housing.